The present disclosure relates generally to an arrangement for, and a method of, enhancing the accuracy of position detection and tracking of a mobile device, such as a handheld data capture reader, a smartphone, a tablet, a computer, a radio, or a like electronic device, that is movable in a venue, such as a retail store, a factory, a warehouse, a distribution center, a building, or a like indoor controlled area.
It is known to deploy a real-time locationing system in an indoor venue, such as a retail store, a factory, a warehouse, a distribution center, a building, or a like controlled area, to determine the location of, and to track, a mobile device, such as a handheld data capture reader, a smartphone, a tablet, a computer, a radio, or a like electronic device. The locationing system includes a transmitter subsystem for transmitting ranging signals to a receiver subsystem in order to locate the mobile device. The ranging signals can be radio frequency (RF) signals, or optical (usually infrared) signals, or acoustic (usually ultrasound) signals. For example, one or more ultrasonic transmitters mounted at fixed locations spaced apart in the venue can be operated to determine the location of a mobile device that carries an ultrasonic receiver. Each ultrasonic transmitter transmits a plurality of ultrasonic ranging signals, preferably as ultrasonic pulses in the 20-22 kHz frequency range. The ultrasonic pulses are received by an ultrasonic receiver, e.g., a microphone, on the mobile device, thereby establishing the presence and the specific location of the mobile device within the venue, typically by using differential flight time techniques known in the art that incorporate triangulation, trilateration, multilateration, and like techniques.
Under ideal operating conditions, the transmitter subsystem periodically transmits the ranging signals directly along direct, non-folded paths to the receiver subsystem. The flight time difference between the transmit time that each ranging signal is transmitted and the receive time that each ranging signal is received along each direct path, together with the known speed of each ranging signal, are used, among other factors, to determine the distance along each direct path, and, in turn, the position of the subsystem mounted on the mobile device, and, in turn, the position of the mobile device.
Yet, the operating conditions of the known locationing systems are sometimes less than ideal. RF, optical and acoustic locationing systems are all subject to multi-path reflections and scattering of their respective ranging signals off various reflecting and/or absorbing surfaces, such as walls, ceilings, floors, curtains, windows, shelves, equipment, and myriad other objects or persons, in the venue. Sometimes their respective ranging signals are so attenuated and weak as to constitute noise. Sometimes their respective ranging signals are blocked or substantially absorbed by such surfaces. For example, optical and acoustic signals do not pass through walls. An RF system may also be subject to interference from stray RF signals. An optical system may also be subject to interference from ambient bright light. An acoustic system may also be subject to interference from ambient loud noise. A ranging signal subjected to such multi-path reflections travels from the transmitter subsystem along an indirect, reflected, folded path to the receiver subsystem. This indirect reflected path is longer than the aforementioned direct path and leads to an erroneous determination of the position of the subsystem mounted on the mobile device.
The known locationing system typically leaves its receiver subsystem turned on and enabled all during its operation. This not only allows the ranging signals traveling along the direct paths, also sometimes referred to herein as “consistent or valid” ranging signals, to be received, but also allows the ranging signals traveling along the indirect reflected paths, also sometimes referred to herein as “inconsistent or invalid” signals, to be received. The signal-to-noise ratio (SNR) of all the ranging signals being received at the receiver subsystem is therefore not optimum due to the receipt of the inconsistent ranging signals.
Accordingly, it would be desirable to dynamically control when and for how long the receiver subsystem is enabled, and to increase and optimize the SNR of the ranging signals being received at the receiver subsystem, with the goal of enhancing the accuracy of position detection and tracking of a mobile device in a venue by a locationing system.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and locations of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The arrangement and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.